Just thought I'd add my experience for those who might benefit. I have just done a visa run to the Thai consulate in Vientiane. Apparently, Monday is not the good day to show up. I can't complain about the service but it was exceptionally busy. guessing over 500 people. apparently Monday is the day all the tours do their visa's. I say this as when you pick your visa up on the Tuesday afternoon, the same 500 people will be there and also at the bridge (on both sides). If you are trying to make the last flight from UTH to CNX (at 18:20) you might be pushed for time unless you were very early in the queue on the Monday morning ( IE before 06:00) I was told that arriving Wednesday for a Thursday Pick up is the way to go.
TLDR : Answer Summary
Sharing personal experience, the individual advises against going to the Thai consulate in Vientiane on Mondays due to high volume, as it's when many tours process visas. They recommend arriving early on Monday before 06:00 or planning to visit on Wednesday for a Thursday pick-up to avoid long queues and make flights schedule easier.
